1. Field of the Invention
This invention relates to a method for the production of acrylic acid polymers. More particularly, this invention relates to the conversion of polyvinyl alcohol to polyacrylic acid wherein the polyvinyl alcohol is reacted with formic acid to convert at least a portion of the hydroxyl groups to formate groups and wherein the formate-containing intermediate is brought into contact with activated carbon in the presence of carbon monoxide, a soluble compound of a group VIII metal catalyst, and an inorganic or organic halide promoter. When substantially all of the hydroxyl groups of the polyvinyl alcohol are converted to formate groups, the final product is polyacrylic acid. When less than all of the hydroxyl groups of the polyvinyl alcohol are converted to formate groups (e.g., by using less than an equimolar amount of formic acid in preparing the intermediate, the final product will be a poly (vinyl alcohol, acrylic acid) copolymer.
2. Prior Art
Wakamatsu et al. in U.S. Pat. No. 3,798,267 discloses the preparation of acetic acid by contacting methyl formate with activated carbon in the presence of a halide promoter and carbon monoxide.
Antoniades U.S. Pat. No. 4,194,056 also discloses a process for the preparation of acetic acid from methyl formate. In accordance with the Antoniades process, the methyl formate is brought into contact with a soluble rhodium salt catalyst in the presence of carbon monoxide and a halogen promoter.
Isogai U.S. Pat. No. 3,839,426 is more broadly directed to the preparation of organic carboxylic acids from formic acid esters, such as vinyl formate (Example 36) by contacting the formic acid ester with a group VIII or group IIb catalyst in the presence of carbon monoxide.
French Patent No. 2,030,118 discloses a process wherein carboxylic acids, especially acetic acid, are produced from methanol by reacting methanol and carbon monoxide over a solid activated carbon bed at a temperature of from 200.degree. to about 500.degree. C. and a pressure of about 100 to about 3000 psi (7-210 Kg/cm.sup.2) using a halogen promoter which is either dispersed on the carbon bed or incorporated as a component of the catalyst system.
Copending coassigned U.S. patent application Ser. No. 478,830 filed Mar. 25, 1983 in the name of John M. Larkin and entitled "A Process for Alkanol Carbonylation to Carboxylic Acids Using the Novel Combination of Catalyst and Carbon Bed Components" discloses a process wherein an alkanol together with a halide promoter and a low concentration of a soluble metal catalyst is passed over a carbon bed in the presence of carbon monoxide.
Copending coassigned U.S. patent application Ser. No. 478,829 filed Mar. 25, 1983 in the name of John M. Larkin and Roger G. Duranleau and entitled "A Process for Producing Carboxylic Acids by Carbonylation of Alkanols Over a Carbon Catalyst" discloses a process wherein an alkanol and a halide promoter are passed over a carbon bed contained in a nickel or cobalt alloy reactor in the presence of carbon monoxide.